The republic was created following the Russian Revolution, by October 29 (some claim 19th) Decree of the Soviet government, Volga German Workers' Commune, giving Soviet Germans a special status among the non-Russians in the USSR. It was upgraded to the status of Autonomous Soviet Socialist Republic on February 20, 1924 [...] It became the first national autonomous unit in the Soviet Union after the Donetsk-Krivoy Rog Soviet Republic. It occupied the area of compact settlement of the large Volga German minority in Russia, which numbered almost 1.8 million by 1897. The republic was declared on January 6, 1924.

[...]
To the moment of declaration of the autonomy an amnesty was announced. However it eventually was applied to a small number of people. According to the politics of korenizatsiya, carried out in 1920s in the Soviet Union, usage of German language was promoted in official documents and Germans were encouraged to occupy management positions. According to the 1939 census, there were 605,500 Germans in the autonomy.

The German invasion of the Soviet Union in 1941 marked the end of the Volga German ASSR. On August 28, 1941, Joseph Stalin issued a formal Decree of Banishment abolishing the ASSR and, fearing they could act as German spies, exiling all Volga Germans to the Kazakh SSR and Siberia. Many were interned in labor camps merely due to their heritage. The Republic was formally extinguished on September 7, 1941.

This is a birth certificate of Georg Meier, born in Dreispitz, Saratov Oblast, Volga. And if you think not only his name, but also the village name sounds surprisingly German, that's because Dreispitz was founded by German protestants in 1767, and those living there were mostly German.

And Drespitz was not alone. There were apparently 104 villages founded there by Germans, and as such there was a large German speaking population in Volga. German may not have been official, but it seems that the Russian and the Soviet authorities in this area provided at least some dual-lingual papers.

interesting though how the German text seems to be primary, the Russian printed after and/or below it. I'd like to see comparison with other ethnicities in the USSR, like Georgian or Armenian areas, see if similar things can be observed there.
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jwentingNov 18 '13 at 9:33

The area that would later be the Baltic States also had a substantial German population, from the days of the Teutonic Knights.
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OldcatSep 5 '14 at 17:25

Let me add to these explanations, and address the question in jwenting's comment.
Soviet Union consisted of 15 republics, each of them had its official language.
According to the constitution, each republic was an "suvereign state", with its own parliament and constitution and had a right of leaving the union (which eventually happened). All documents were written in two languages: local and Russian (except in one republic, Russia). In addition
to these republics there were smaller units: autonomous republics, autonomous regions, and autonomous districts. With smaller degree of autonomity than principal republics. German autonomous republic was abolished during WW II. But at least in the beginning (before WW II),
all these smaller units used their own languages for all kinds of documentation.

So, to answer the original question: yes, German was an official language in a part of USSR, from the creation of USSR until WW 2.

Wikipedia article on Soviet constitution also has links to earlier versions. But the principle that this is the union of independent states was established from the very beginning. This is exactly what made possible the peaceful dissolution of the union.
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AlexDec 20 '13 at 18:37

Three of the republics even had their own separate UN representation. Stalin wanted all 15 to have it, but the other parties founding UN objected:-)
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AlexDec 20 '13 at 18:40

Please cite an article of a constitution that claimed that a soviet republic to be an independent state.
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AnixxDec 20 '13 at 18:44